1. Field of the Invention
The present invention relates to a bus system for configuring communication interfaces in a vehicle having at least two different bus lines, the two bus lines each being electrically coupled to one and the same first voltage-limiting means to limit the voltage level of a voltage pulse occurring with a predefined reference potential as a positive voltage pulse between one of the two bus lines and a first point. The present invention also relates to a method for manufacturing such a bus system. In addition, the present invention relates to a vehicle having such a bus system.
2. Description of the Related Art
When communication interfaces are configured in vehicles, bus systems, respectively fieldbus systems, such as CAN or LIN bus systems are used, for example. In terms of electrostatic discharge (ESD) and electromagnetic compatibility (EMC), stringent demands are placed on such bus systems and the connections thereof. Moreover, the lines present in such a bus system must also allow the occurrence of voltages that reside far below the vehicle ground and can typically be down to −27 V.
From the related art, it is known to use CAN bus systems that have the electrostatic discharge protection structure shown in FIG. 1 for configuring communication interfaces in the vehicle.
Two-conductor CAN bus system 10 shown in FIG. 1 includes a first bus line, respectively CAN_H line 20 and a second bus line, respectively CAN_L line 30. Via a coupling diode 40, which is directly connected at the anode thereof to corresponding bus line 20, 30, the two bus lines 20, 30 are each routed to one and the same electrostatic discharge protection 50 for positive voltage pulses. Coupling diodes 40 are each configured as coupling diodes having a non-isolated drain.
Electrostatic discharge protection 50 for positive voltage pulses includes a first voltage-limiting means for limiting the voltage level of a voltage pulse occurring as a positive voltage pulse between one of the two bus lines 20, 30 and a ground 60. The first voltage-limiting means includes a suppressor diode (positive clamp) 70, which is directly connected at the cathode thereof to the cathodes of the two coupling diodes 40 and, at the anode thereof, directly to ground 60. Suppressor diode 70 becomes conductive when a voltage pulse occurring as a positive voltage pulse between one of the two bus lines 20, 30 and ground 60 has a voltage level that exceeds that of the breakdown voltage of suppressor diode 70. The current generated by such a positive voltage pulse is then safely conducted by suppressor diode 70 to ground 60. This prevents any build up of voltage that occurs as positive destructive voltage.
Bus lines 20, 30 are each routed to another electrostatic discharge protection 51, 52 for negative voltage pulses. A dual configuration of electrostatic discharge protection 51, 52 for negative voltage pulses is realized, i.e., an electrostatic discharge protection 51, 52 is additionally provided for each of bus lines 20, 30.
Each electrostatic discharge protection 51, 52 for negative voltage pulses includes a second voltage-limiting means for limiting the voltage level of a voltage pulse occurring as a negative voltage pulse between one of corresponding bus lines 20, 30 and a corresponding ground 61, 62. In this case, the second voltage-limiting means each includes a suppressor diode (negative clamp) 71, 72, which is directly connected at the anodes thereof to corresponding bus line 20, 30.
Each of the two suppressor diodes 71, 72 is directly connected at the cathode thereof to a corresponding reverse polarity diode 41, 42. Each of reverse polarity diodes 41, 42 is then directly connected at the anode thereof to a corresponding ground 61, 62. Each of the two suppressor diodes 71, 72 becomes conductive when a voltage pulse occurring as a negative voltage pulse between corresponding bus line 20, 30 and corresponding ground 61, 62 has a voltage level that exceeds that of the breakdown voltage of corresponding suppressor diode 71, 72. The current generated by such a negative voltage pulse is then safely conducted by corresponding suppressor diode 71, 72 to corresponding ground 61, 62. This prevents any build up of voltage that occurs as negative destructive voltage.
Electrostatic discharge protection 51, 52 for negative voltage pulses cannot be provided in the way that electrostatic discharge protection 50 can for positive voltage pulses. The reason is that the cathodes of such coupling diodes 40, which are configured with a non-isolated drain, cannot be directly hanged on bus lines 20, 30 because they do not allow the occurrence of negative voltage pulses that reside far below the vehicle ground and can be down to −27 V. For this reason, a dual configuration of electrostatic discharge protection 51, 52 for negative voltage pulses is required by way of electrically coupled reverse polarity diodes 41, 42, as described earlier.
Disadvantageous in this context is that considerable surface area is consumed since the ESD protective structure for negative voltage pulses is provided twice. A relatively large ESD protective structure must be used since currents of up to 32 A can flow in the case of the 8 kV plasma gun model. Moreover, the double design of the electrostatic discharge protection structure for negative voltage pulses leads to rectification effects when EMC, respectively DPI (direct power injection) measurements are performed. A frequently occurring consequence is that components designed in this manner do not pass the certification needed for original equipment manufacturer (OEM) requirements.